Cream depilatory and process for preparing same



preparing same. vision of a cream depilatory of good stability,

tein.

- marked degree.

Patented Nov. 8, 1949 CREAM DEPILATORY AND PROCESS FOR PREPARING SAME Jonas Kamlet, New York, N. Y.

No Drawing.

Application February 24, 1948,

Serial No. 10,582

2 Claims. (01. 167-89) The present invention relates to a cream depilatory and to the process for preparing same.

More particularly, it relates to a depilatory preparation in cream or paste form suitable for use on the human skin '(as, for instance, in the removal of hair from the forearms, legs, armpits,

etc.) and to a simple and eflicient process for It has for its purpose the prohigh cosmetic acceptability, low cost and rapid effectiveness which is devoid of many of the disadvantages of previous preparations of this nature and which will remove hair from the human skin with safety, speed and facility.

While mechanical depilatories (such as waxes and resins applied while warm and then removed upon cooling) are known and used to some extent, most of the depilatories in common use at the present time are chemical in nature.

The reaction mechanism of these chemical depilatories is fairly well known. Marriott (Journ. Intern. SoqLeather Trades Chem. 17, 178-193 (1933)) and others have pointed out that the beginning of efiective depilation occurs when the disulfide linkages in the cystine component of the keratin molecule in hair are reduced. When these disulfide linkages of the cystine are broken, the combination of the free sulfhydryl degradation products with the alkali hair and ultimate disintegration.

Thus, an effective depilatory must contain (a) a reducing agent sufficiently potent to reduce the disulfide linkages of cystine in the hair to to cause the sw lling of a reduced keratinous pro- The most commonly used reducing agents in cosmetic depilatories have heretofore been the earths, The alkali metal sulfides hydrolyze quite readily to give equilibrium mixtures containing alkali metal hydrosulfides, which are good reducing agents and excellent depilatories, but the alkali metal hydroxides formed as concomitants are excessively caustic and irritating to the human skin. The alkali metal hydrosulfides per so are used to some extent in conjunction with alkali earth metal hydroxides, but their use in cosmetic depilatories is limited by their poor stability and their excessive hydrogen-sulfide odor.

The alkali earth metal sulfides, however, do not possess these disadvantages to the same Thus, barium sulfide and strontium sulfide are relatively stable and not excessively malodor-ous. 'When suspended in water, these alkali earth sulfides hydrolyze to form equilibrium mixtures of alkali earth metal hydrosulfide and alkali earth metal hydroxide:

The alkali earth metal hydrosulfides thus formed serve as potent reducing agents, while the alkali earth metal hydroxides provide the alkalinity required for effective depilation.

In terms of hydrogen ion concentration, no depilation will occur at a pH below 11. For rapid and effective epilation, a pH of 12 to 13 is required (De Navarre, The Chemistry and Manu- 5 facture of Cosmetics, D. Van Nostrand Co. 1941) page 535. A saturated aqueous solution of Ca(OH)2 has a pH of 12.4; a saturated aqueous solution of Sr(OH)2 has a pH of 12.9; a 0.1 N

(1.58%) aqueous solution of Ba(OH)2 has a pH While used to some extent in cosmetic depilatories, barium sulfide has the disadvantage of being poisonous, whereas strontium sulfide is excessively expensive and often difliculty available.

5 Bothof these compounds have rather high molecular weights so that comparatively large quantities of either must be employed to obtain an effective concentration of active sulfhydryl group. Thus, pure barium sulfide contains only 18.9% of present in the depilatory causes swelling of the 3 Sill-fur and P Strontium Sulfide Contains y of commerce often contain as little as 65% of the pure sulfide, the remainder being inert incysteine, and (b) an agent of sufficient alkalinity 'gred-ients.

Calcium sulfide would indeed be the ideal depilating agent. The compound is cheap and readily available in large amounts. When pure,

" calcium sulfide contains 441.5% of sulfur. Howsulfides and the hydrosulfides of the alkaline so ever, when technical calcium sulfide is used in terial or by the fusion of lime and sulfur, both at advanced temperatures (Ullmanns Enzyklopaedie der Technischen Chemie, volume 3, page 58, 1929). When preparedin this manner, calcium sulfide forms a'yell'owish to light-gray powder. Upon suspension in water, it fails to hydrolyze to calcium hydrosulfide and calcium hydroxideas might be expected:

2CaS+2H2O Ca(SH)2+Ca(OH)2 -This unforeseen behavior may be attributed to the {deposition of a surface layer of poorly soluble each discrete particle of calcium sulfide. In other words, the hydrolysis does commence when the calcium sulfide is suspended in water, but is prevented from proceeding to the building up of an effective concentration of calcium hydrosulfide by the accumulation of an insoluble or poorly soluble film of calcium hydroxide at the water-solid interface, which film prevents further solution and hydrolysis.

To overcome this difiiculty, it becomes necessary to prepare the calcium hydrosulfide-calcium hydroxide couple in aqueous solution-suspension, rather than by hydrolysis of preformed calcium sulfide. Thus, Donner (U. S. Patent 1,379,855, 1921) passes hydrogen sulfide gas into an aqueous suspension of milk of lime to obtain the desired equilibrium mixture of calcium hydrosulfide and calcium hydroxide. Related preparative procedures are described by Divers and Shimidzu (Journ. Chem. Soc. (London) 45, 270 (1884)) and by Hartman (Canadian Patent 438,318 (1946)). From a practical point of view, this procedure has many disadvantages:

(a) Hydrogen sulfide is noisome and a noxious gas and its use in a cosmetic manufacturing plant is highly undesirable;

(17) Because of the insolubility of the calcium hydroxide, the uniform gassing of a slaked lime suspension is not usually feasible. so that duplicate batches of Ca(SH)z Ca(OH)z are rarely of identical composition;

Unless accurate control of the gassing is feasible, there is often the danger of carrying the process too far and thus imparting a most undesirable hydrogen sulfide odor to the finished product;

(:1) Chemical lime usually contains traces of heavy metal compounds such as iron oxides, etc., which impart to the finished depilatory product most undesirable gray, green or blue off-colorations due to the highly-colored heavy metal sulfides formed by interaction with the hydrogen sulfide.

It is a purpose of the present invention to provide a cream depilatory based on a manufacturing procedure which takes advantage of the high elfectiveness of depilatories based on calcium calcium hydroxide on 4 Patent 1,973,130 934)). These are usually excessively malodorous and therefore unsuited for cosmetic purposes;

(0) The alkaline salts of thioglycollic acid (Fletcher, French Patent 824,804 (1938); B0- heman, British Patent 484,467 (1938) Evans and McDonough, French Patent 844,629 (1939) U. S. Patent 2,352,524 (1944). While these depilatories represent a considerable advance in the cosmetic art, they are still considerably more expensive than those based on calcium hydrosulfide-calcium hydroxide, and are excessively subject to inactivation by the oxygen of the air,

' which converts the thioglycollic acid derivative to inactive thio-diglyoollic acid and dithio-diglycollic acid derivatives;

(d) Sodium selenide Deutsche Parfumerie, 17,316 effective depilatory, cessively toxic.

The basis of the present invention is my finding that an excellent depilatory preparation can be based on the products obtained by the reaction of a solution of a water-soluble sulfide and a solution of at least an equimolecular quantity of a water-soluble calcium salt. Thus, when an aqueous solution of a water-soluble sulfide is mixed with a solution of at least an equimolecular quantity of a water-soluble calcium salt, there is no precipitation of calcium sulfide as might be expected. Instead, there is formed the following equilibrium mixture:

where M is an equivalent of the cation of the water-soluble sulfide and X is an equivalent of the anion of the water-soluble calcium salt, This equilibrium mixture contains both of the com- (NazSe), (Silman, (1931) which is an but quite unstable and exponents necessary for eifective depilation, i. e.

hydrosulfide-calcium hydroxide, their low cost, 7

their lack of excessive causticity and irritating effects on the human skin and their high effective sulfhydryl concentrations but which obviates completely (a) the necessity of gassing a lime suspension with hydrogen sulfide, (b) the lack of uniformity in previous products of this nature, (0) the marked hydrogen sulfide odor of improperly gassed batches, (d) as much as possible, the oil-colored heavy metal sulfide impurities, (e) the noisome and noxious features of the previous manufacturing procedures, and such other objections which have previously been attributable to the group of depilatories based on calcium hydrosulfide-calcium hydroxide,

Other reducing agents have also been used in cosmetic depilatories in place of the alkali earth metal sulfides and hydr-osulfides. Among these may be mentioned:

(a) The alkaline stannites (Stoddard and Berlin, U. S. Patents 2,123,214 (1938); 2, 99,249 (1940) McKee and Morse, U. S. Patent 1,899,707 (1933)). These are excessively unstable and require too high alkalinity and too long a contact period on the skin for effective cosmetic use;

(b) Alkyl and aryl mercaptans in alkaline media (Jaeger and Herrlinger, U S. Patents 2,169,147-8 939); Turley and Windus, U S.

the reducing agent-calcium hydrosulfide, and the alkaline agent-calcium hydroxide, which gives the medium the necessary pH between 12 and 13 without being excessively caustic and irritating to the human skin.

Typical examples of water-soluble sulfides effective in the process of the present invention are sodium sulfide, ammonium sulfide, potassium sulfide, lithium sulfide, and organic sulfides such ethanolammonium sulfide, diethanolammonium sulfide, triethanolammonium sulfide, ethylene diammonium disulfide, morpholinium sulfide, methylammonium sulfide, etc., etc. The preferred product for the present invention is a fiaked sodium sulfide, substantially free of iron and other heavy metal impurities, assaying 60%-61% NazS, such as is marketed by the Barium Reduction Company, south Charleston, West Virginia.

Typical examples of water-soluble calcium salts efiective in the process of the present invention are calcium chloride, calcium bromide, calcium iodine, calcium nitrate, calcium nitrite, calcium acetate, calcium gluconate, calcium levulinate, etc., etc. The'preferred product for the present invention is the technical, flaked calcium chloride obtained as a uniform, lowpriced lay-product from the Solvay soda ash process and assaying 75 %77% of calcium chloride, corresponding to CaCl2.2H2O.

The concentrations of water-soluble sulfide in the finished cream depilatory may vary from 0.08 gram-mole to 1.50 gram-moles per kilogram of product, but the preferred concentration for a. speedy, effective and safe "depilation is from to the finished depilatory product.

It will thus be recognized that by the simple expedient of mixing two easily-prepared solutions oi readily available and inexpensive chemicals? (a) ,An. equilibrium mixture containing calcium hydrosulfide, calcium hydroxide and. basic calciumhydrosulfide [Ca'(SII) (011)] is prepared without the necessity of gassing a suspension of lime with hydrogen sulfide; V

(b) A product of invariable uniformity can be obtained;

An excess of malodorous hydrogen sulfide in the product is avoided;

If the sulfide is (d) Off-colors in the finished product can be avoided by the use of starting materials substan-' tially free of heavy metal impurities which form colored sulfides;

(e) The use of the dangerous and noisome hydrogen sulfide gas as well as all of the equipment, cylinders, measuring devices, safety precautions, etc., required in previous methods is entirely obviated; and

(I) An inexpensive product of high depilating effectiveness is obtained.

The other components of the cream depilatories of the present invention are: (a) a filling agent or diluent, (b) a bodying and bonding agent and (c) optionally, a perfuming agent.

The filling agents or diluents may be chosen from among the chemically inert products well known and widely used for this purpose in the formulation of cosmetics. These include calcium carbonate (precipitated chalk), finely divided silica, strontium carbonate, barium sulfate, lithopone, gypsum, talcum, kaolin, magnesium carbonate magnesium oxide, kieselguhr, zinc oxide, bentonite, titanium dioxide, magnesium trisilicate, etc. All of these agents are stable, inert to the components of the depilatory at the pH of the product, inexpensive and readily available.

Evans (British Patent 451,611) has shown that the nature of the filler or diluent has a considerable, effect on the time required to obtain effective depilation with strontium sulfide. I have also found that the use of calicum carbonate (precipitated chalk) as afilling agent in the products of the present invention produces a quicker and more effective depilating product than any other agent. This is highly advantageous since calcium carbonate is freely available in a state of uniformly great purity and at a low cost. It is therefore the preferred filling agent in these products.

The bodying and bonding agent may be chosen from among the following products: fatty alcohols, such as cetyl, lauryl, stearyl, etc., soaps such as sodium stearate, sodium myristate, etc., bentonite, cellulose ethers such as methyl cellulose, sodium cellulose glycollate (sodium carboxymethylcellulose), silica gel; alumina gel, etc., etc. In general, these bonding and bodying agents must be inert to the reducing agents in the depilatory;indefinitely stable at a pH of 12 to v13 and 'capable of beingfrozen and thawed a number of times. without ibre-aking. Perhaps the best of these is methylfcellul'ose, which. is the preferred bodying:and'bondingagent for the products of the present invention.

The perfuming agents must be chosen very carefully in. the light of the high reactivity of calcium hydrosulfide with many reducible organic compounds "often. used in the formulation of perfumes; Nitro compounds, such as the synthetic musks, are, therefore; counterindicated. Thehigh alkalinity of the preparation (pl-I 12-13) makes it inadvisable to'use the readily'saponifiable esters or readily aldolizab'le-aldehvdes. The presence of. the -SH' grouping. may further cause certain alcohols to be-fconverted to malodorous mercapta'nsal In generaLthe best perfuming agents for products of this nature are based on terpenes and other hydrocarbons," some types 'of' unreactive alcohols, ethers;v .ketones and on such specific perfuming agents such as the. oils of vetivert, patchouli, thyme, lavender, lemon, citronella, cedarleaf, caraway, sandalwood and petitgrain and on synthetics such as ionone, safrole, vanillin, menthol, diphenyl'methane, diphenyl oxide, betanaphthyl methyl ether, methyl acetophenone, isoamyl benzyl ether, terpineol, anethol, geraniol, etc., etc. 7

The concentrations of filling agent, bodying and bonding agent and perfume are so chosen as to give the finished depilatory formulation the proper consistency and texture. The finished product may be dispensed in tubes, jars, tins or in any convenient container the coating of which is not reactive with the components of the depilatory.

The products of the present invention will effect a safe and complete depilation when allowed to remain on the area to be dehaired for four to ten minutes, and usually in from four to five minutes. They are non-toxic, devoid of irritating effects and completely safe to employ. V

The following example describes a typical depilatory composition of the present invention and the process of preparing the same. It is given by Way of illustration and is not intended'to limit this invention to reagents, proportions or conditions described therein. Obvious improvements will occur to any person skilled in the art.

Example 50.0 grams of sodium sulfide flakes, iron-free, assaying 60%-61% of NazS (0.385 mole) is dissolved in 375.0 0. o. of cold distilled water. At the same time, 60.0 grams of calcium chloride, technical flakes, assaying '75%77% of CaClzl (0.405 mole) is dissolved in 90.0 c. c. of cold, distilled water. The calcium chloride solution is added with constant stirring to the sodium sulfide solution, whereby a uniform mixture is obtained. A total of 275.0 grams of lightweight, cosmetic grade precipitated chalk (calcium carbonate) is now added in small portions to the well-stirred mixture, care being taken to wet each portion of the precipitated chalk before the next is added. After all the precipitated chalk has been stirred into the mixture, there is added 150.0 grams of a 10% (weight-for-weight) gel of methyl cellulose (400 centipoise viscosity) in water, and the mixing is continued for at least thirty minutes or until a completely uniform, homogeneous cream is obtained. Five to twenty grams of a suitable perfume oil is now added, and

the mixture is stirred for another twenty to thirty minutes until completely smooth and uniform.

The resultant ivory to light grey colored cream depilatory may then be'packaged in tubes, jars or tins, as desired. It will remain stable and effective when stored for prolonged periods of time under the usual conditions of shelf life.

This product is used in the manner usually employed with cream depilatories. The area to be depilated is covered with the preparation to a depth of 1 to 3 millimeters. For light hair, four to five minutes usually sufiice; medium hair may require five to six minutes and coarse hair may require six to eight minutes of application of this 1 product. At the end of this period, the depilatory paste is taken off by washing or by gentle me- -chanical removal and the depilated area is washed thoroughly with Water until completely clean and devoid of remnants of hair or depilatory.

Having described my invention, what I claim and desire to protect by Letters Patent is:

1. A process for the manufacture of a cream depilatory which comprises mixing, per kilogram of finished product, 0.08 to 1.50 gram-moles of a water-soluble sulfide, at least an equimolar concentration of a water-soluble calcium salt and sufiicient quantities of a filling agent, a bodying and bonding agent and a perfuming agent, to

comprise the difference.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 450,032 Perl Apr. 7, 1891 615,705 Holmes Dec. 13, 1898 631,405 Payne Aug. 22, 1899 1,379,855 Donner May 31, 1921 2,352,524 Evans June 27, 1944 OTHER REFERENCES Kalish: Cosmetic Manual, Drug and Cos metic Industry, Aug. 1940, pages 148-150.

Alderton: Some Problems In Liming, The Leather World, 1944, vol. 36, pages 316, 317, 396, 

